Yokogawa 415 Steam and Gas - Manual (Page 18)

3.2 FLOW EQUATIONS FOR GASES
This section applies only to gas flow measurement and, if the Model 415 is to be
used for steam measurement, the reader can skip this section and go to section
3.3.
The Model 415 will accept inputs from a wide range of flowmeters with the
flowrate calculated by the equations defined below. Both mass flow and volume
corrected flow to a base temperature and pressure are calculated and displayed in
either SI (metric) or US units. For an explanation of the symbols used in the
equations see the list at the beginning of this manual.
Two basic formulae are common to all equations:
1. Specific Gravity, G =
Molecular Weight of Gas
Molecular Weight of Air
.....(1) =
Molecular Weight of Gas
28.9625
2. Density of a Gas,
ρ
, at base conditions:
In SI Units
kg/m 3 .....(2)
ρ
B
=
3.4834 G P
B
Z
B
T
B
In US Units
lbs/ft 3 .....(3)
ρ
B
=
2.6988 G P
B
Z
B
T
B
Standard Conditions
Standard conditions are defined as:
15°C (288.15°K) and 101.325 kPa
or 59°F (518.67°R) and 14.69595 psia.
16 Operation